An important challenge for the future growth of the Internet is to design routers that can forward the exponentially increasing volume of traffic, and at the same time provide the service differentiation needed by new applications. In this paper, we describe the architecture, implementation, and initial experiences with a system designed to meet this challenge. This system, which we call a QoS capable switch-router (QSR), combines the salient features of switching and routing technologies to provide high throughput and support the different classes of service being defined by the IETF. It consists of a core (ATM) switch fabric connecting intelligent adapters, each capable of both routing and switching pockets. A control engine is responsible for routing, RSVP signalling, and resource management. We have built a prototype network of 3 systems connected to several UNIX hosts, and have conducted preliminary performance measurements on this network.

We study a class of all-optical networks using wavelength-division multiplexing (WDM) and wavelength routing, in which a connection between a pair of nodes in the network is assigned a path and a wavelength on that path. Moreover, on the links of that path no other connection can share the assigned wavelength. Using a generalized reduced load approximation scheme we calculate the blocking probabilities for the optical network model for two routing schemes: fixed routing and least loaded routing.

Consider a switching component in a packet-switching network, where messages from several incoming channels arrive and are routed to appropriate outgoing ports according to a service policy. One requirement in the design of such a system is to determine the buffer storage necessary at the input of each channel and the policy for serving these buffers that will prevent buffer overflow and the corresponding loss of messages. In this paper, a class of buffer service policies, called Least Time to Reach Bound (LTRB), is introduced that guarantees no overflow, and for which the buffer size required at each input channel is independent of the number of channels and their relative speeds. Further, the storage requirement is only twice the maximal length of a message in all cases, and as a consequence the class is shown to be optimal in the sense that any nonoverflowing policy requires at least as much storage as LTRB.

A design is proposed for an n*n switch to be used in frame relay networks. The design is based on a single storage unit for packets and hardware-based mechanism for handling simultaneously arriving packets over different input channels which may be intended for the same output channel. The switch is flexible in that it can handle variable length packets, a large number of input/output channels, and a wide range of channel speeds. It can perform cut-through switching and thus decrease packet delay through the network. It allows the design of high-throughput frame-relay nodes, simplifying the design and management of large networks. Its use of a hardware-implemented dynamic scheme for allocating storage allows efficient utilization of buffer space.>

System correctness often presents itself as the problem of showing that two programs, the "specification" and the "implementation," are in some sense equivalent. Such a concept of equivalence is supplied by Milner's definition of simulation between programs. This paper presents a problem-reduction approach to proving simulation, and describes an interactive system designed for this purpose.